a(n) is the total number of paths starting at (0,0), ending at (n,0), consisting of steps (1,1), (1,0), (1,-2), and staying on or above y = -1.

A378849

a(n) is the total number of paths starting at (0,0), ending at (n,0), consisting of steps (1,1), (1,0), (1,-2), and staying on or above y = -1.

Terms

    a(0) =1a(1) =1a(2) =1a(3) =3a(4) =9a(5) =21a(6) =48a(7) =120a(8) =309a(9) =787a(10) =2011a(11) =5215a(12) =13652a(13) =35894a(14) =94823a(15) =251889a(16) =672285a(17) =1801185a(18) =4842757a(19) =13064059a(20) =35349463a(21) =95912989a(22) =260896318a(23) =711338596a(24) =1943690464a(25) =5321704006a(26) =14597781706a(27) =40112702176a(28) =110404515703a(29) =304338523999

External references